A resource I located re: "Requirement" (in the context of "software
requirements") is at [1].
Note that it is said in the "Testability" section that
"Most requirements should be testable. If this is not the case, another
verification method should be used instead (e.g. analysis, inspection or
review of design). Testable requirements are an important component of
validation.
Certain requirements, by their very structure are not testable. These
include requirements that say the system shall never or always exhibit a
particular property. Proper testing of these requirements would require an
infinite testing cycle. Such requirements are often rewritten to state a
more practical time period.
Untestable non-functional requirements may still be kept as a documentation
of customer intent; however they are usually are traced to by process
requirements that are determined to be a practical way of meeting them."
Thanks and best wishes
Tim Boland
[1]: http://en.wikipedia.org/wiki/Requirement
>* Dominique Hazael-Massieux wrote:
> >Is there a logical contradiction behind the idea of a normative
> >requirement that would not be testable? I don't think there is, but
> >would be interested to hear what others think about it.